/*
 * Copyright © 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;

namespace Spring.Core;

/// <summary>
/// Comparator implementation for <see cref="Spring.Core.IOrdered"/> objects, sorting by
/// order value ascending (resp. by priority descending).
/// </summary>
/// <remarks>
/// <p>
/// Non-<see cref="Spring.Core.IOrdered"/> objects are treated as greatest order values,
/// thus ending up at the end of a list, in arbitrary order (just like same order values of
/// <see cref="Spring.Core.IOrdered"/> objects).
/// </p>
/// </remarks>
/// <author>Juergen Hoeller</author>
/// <author>Aleksandar Seovic (.Net)</author>
[Serializable]
public class OrderComparator : OrderComparator<object>, IComparer
{
}

/// <summary>
/// Comparator implementation for <see cref="Spring.Core.IOrdered"/> objects, sorting by
/// order value ascending (resp. by priority descending).
/// </summary>
/// <remarks>
/// <p>
/// Non-<see cref="Spring.Core.IOrdered"/> objects are treated as greatest order values,
/// thus ending up at the end of a list, in arbitrary order (just like same order values of
/// <see cref="Spring.Core.IOrdered"/> objects).
/// </p>
/// </remarks>
/// <author>Juergen Hoeller</author>
/// <author>Aleksandar Seovic (.Net)</author>
[Serializable]
public class OrderComparator<T> : IComparer<T>
{
    public static readonly IComparer<T> Instance = new OrderComparator<T>();

    /// <summary>
    /// Compares two objects and returns a value indicating whether one is less than,
    /// equal to or greater than the other.
    /// </summary>
    /// <remarks>
    /// <p>
    /// Uses direct evaluation instead of <see cref="System.Int32.CompareTo(object)"/>
    /// to avoid unnecessary boxing.
    /// </p>
    /// </remarks>
    /// <param name="o1">The first object to compare.</param>
    /// <param name="o2">The second object to compare.</param>
    /// <returns>
    /// -1 if first object is less then second, 1 if it is greater, or 0 if they are equal.
    /// </returns>
    public virtual int Compare(T o1, T o2)
    {
        IOrdered o1lhs = o1 as IOrdered;
        IOrdered o2rhs = o2 as IOrdered;
        int lhs = o1lhs?.Order ?? int.MaxValue;
        int rhs = o2rhs?.Order ?? int.MaxValue;
        if (lhs < rhs)
        {
            return -1;
        }

        if (lhs > rhs)
        {
            return 1;
        }

        return CompareEqualOrder(o1, o2);
    }

    /// <summary>
    /// Handle the case when both objects have equal sort order priority. By default returns 0,
    /// but may be overriden for handling special cases.
    /// </summary>
    /// <param name="o1">The first object to compare.</param>
    /// <param name="o2">The second object to compare.</param>
    /// <returns>
    /// -1 if first object is less then second, 1 if it is greater, or 0 if they are equal.
    /// </returns>
    protected virtual int CompareEqualOrder(T o1, T o2)
    {
        return 0;
    }
}
